The present disclosure relates to memory systems. A semiconductor memory device may be volatile or nonvolatile. A nonvolatile semiconductor memory device may retain contents stored therein even at power-off. Data stored at the nonvolatile semiconductor memory device may be permanent or reprogrammable according to a memory manufacturing technology. The nonvolatile semiconductor memory device may be used to store programs, micro codes, user data in a wide range of applications such as computers, avionics, communications, consumer electronics, and so on.